Within Spinoza's System (laid down in the Ethics), the difference of inadequate from adequate knowledge is crucial. Perhaps it is even the central cornerstone of his system, because adequate knowledge seems to be both a necessary and sufficient condition to attain virtue, happiness, blessedness. Without Spinoza's theory of adequate knowledge, his system could not rightly be called Ethics, because adequate knowledge, and adequate knowledge alone, grounds the possiblity of an ethical life.

I wonder, however, how Spinoza's view on adequate knowledge can be both so central and so sketchy, that it seems not only to evade my grasp, but also that of all of the commentators I've read. I just don't understand what adequate knowledge is. For Spinoza, it evidently comprises two sorts of knowledge and at least this point shouldn't be subject to debate: the second kind of knowledge is knowledge of the common notions while knowledge of the third kind is intutitive knowledge. But - and here things start to get messy - how can Spinoza claim to have knowledge of these kinds without being rightly called a dogmatist? I don't see much hope for Spinoza to evade this reproach, even though I would like to see him avoid it.

  • See Spinoza’s Method for Epistemology with references. Jan 10, 2020 at 14:26
  • Maybe useful: Richard Mason Spinoza : Logic, Knowledge and Religion (2016, Routledge), Part II. Knowledge. Jan 10, 2020 at 14:33
  • The IEP article is very elucidating concerning the overall architecture of Spinoza's epistemology, but it leaves out the details. For example, common notiones appear mainly in EIIP37-39 and it is quite hard to understand for example Spinoza's proof of his assertion that the common notions can only be conceived adequately (P38). If we assume that a common notion is a universal property of modes conceived under a given attribute (as defined in the IEP article), what can it mean for such properties to be necessarily conceived adequately? I'm a bit lost here. Jan 10, 2020 at 17:13
  • Abraham has an interesting take in Spinoza's Concept of Common Notions: "thinking functional when saying adequate brings us to the root of what Spinoza calls a common notion", adequate thought understands some common function. But on the "proof" he only says that it follows from Spinoza's definition of the essence, which involves "hair-splitting diferentiations that may seem incomprehensible and even paradoxical at first reading yet grow upon you and become quite self-evident as your study of ETHICS II progresses".
    – Conifold
    Jan 11, 2020 at 5:01
  • The context is Descartes' philosophy; we have "adequate knowledge" of e.g. mathematical truths, and the criteria of "clearness and distinctness" give us a way to achieve adequate knowledge of God and so on. Having said that, what do you mean with "dogmatist" ? Spinoza, as well as D, was not an empiricist for sure... Jan 11, 2020 at 9:29

1 Answer 1


A full answer to your question would be very difficult here but there is a reasonably straightfoward account in the Ethics of how one type of 'adequate knowledge' is possible. This account is not dogmatic in my view.

Three grades of knowledge

The three grades of knowledge are readiy set out. There is knowledge:

  1. From signs; as for example when we hear or read certain words, we recollect things and form certain ideas of them similar to them, through which ideas we imagine things [Schol. Prop. 18, pt. 2]. These two ways of looking at things I shall hereafter call knowledge of the first kind, opinion or imagination.

  2. From our possessing common notions and adequate ideas of the proper- ties of things [Corol. Prop. 38, Prop. 39, with Corol. and Prop. 40, pt. 2]. This I shall call reason and knowledge of the second kind.

Besides these two kinds of knowledge, there is a third, as I shall hereafter show, which we shall call intuitive science [intuitive knowledge: GT]. This kind of knowing advances from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the essence of things.

(Spencer Carr, 'Spinoza's Distinction Between Rational and Intuitive Knowledge', The Philosophical Review, Vol. 87, No. 2 (Apr., 1978), pp. 241-252: 242.)

Second grade of knowledge

The first grade of knowledge apppears a plausible candidiate, and might on its own rebut the charge of dogmatism. As regards the second grade of knowledge, Spinoza tells how we form common notions (notionum communium). Common notions are necessarily adequate and constitute knowledge albeit only of the second kind:

They are common notions are structural features that all modes within an attribute share (E2P38; the corollary appeals to Lemma 2, which in turns follows from the definition of a body E2D1).

(Eric Schliesser, 'Spinoza on the Politics of Philosophical Understanding', Proceedings of the Aristotelian Society, New Series, Vol. 111 (2011), pp. 497-518 Published by: Oxford University Press on behalf of The Aristotelian Society: 512.)

In propositions 37-40 of Part II Spinoza explains that we can form common notions from our perceptions of objects and that these notions are necessarily adequate. His idea is, roughly, that all bodies [modes: GT], by virtue of involving the conception of the same attribute, agree in certain respects; every body and every part of every body has something in common. Spinoza's view of the relationship between mind and body and his doctrine of perception lead him to hold that any such common notion can only be perceived adequately. (At IIP13L2 Spinoza gives "being capable of motion and rest" as an example of what is common to all bodies.) The first scholium to proposition 40, the scholium just preceding the classification, is concerned with distinguishing these common notions from universal ideas drawn from experience which we might confuse with common notions. Throughout, Spinoza is talking about how we do and how we should handle our experience of natural objects.

(Carr: 245.)

I omit conisideration of the third grade of knowledge, intuitive knowledge or scientia intuitiva, for two reasons. In the first place it raises difficulties which cannot be dealt with briefly; and secondly, the task was to counter the criticism that Spinoza's account of adequate knowledge is dogmatic. In presenting a case that the first and second grades of knowledge have argumentative support in Spinoza's text and are not merely assertively claimed, I believe I have vindicated him against the charge of dogmatism. This is not to say that Spinoza's arguments are correct as they stand. I do not need to show that the arguments are cogent, only that they are arguments which as such give the slip to the censure of dogmatism.

  • Thanks for your cogent summary. I'd like to dismiss the thought that Spinoza is a dogmatist concerning the common notions, because - as you have shown - he does provide arguments for his views. He can show that a) there must be common notions (by EIIL2 and EIIP7) and b) that common notions must be perceived adequately (by EIIP38). However, wouldn't you agree that Spinoza does not provide an acount of how common notions can be perceived at all? In EIIP39d he asks what happens, if "the human body is affected by an external body through that, which it has in common therewith". Jan 12, 2020 at 11:47
  • But how can one be affected by something, which is a general property? This to me seems a bit mysterious and I have no idea how the process of forming common notions proceeds in detail. Jan 12, 2020 at 11:47
  • And as long he does not provide a convincing account of how this process happens in detail, the mere assurance that it does occur has an air of dogmatism about it - don't you think? Jan 12, 2020 at 11:48
  • Moritz Wolff. Thank you for your careful attention to my answer. I'd reply to your last comment as follows. Dogmatism is present not when one's arguments fail - and I didn't mean to commit myself to the cogency of Spinoza's arguments - but when a claim is made without argument or when (hardly possible in a posthumous text) a relevant objection is ignored. I can't see that the Spinoza of my answer is a dogmatist on either score.
    – Geoffrey Thomas
    Jan 12, 2020 at 12:45
  • 1
    This is a valid and important matter but doesn't it need a separate question? This I invite you to put. I was simply responding to the charge of dogmatism which for the purpose of discussion you now set aside and that's fine. You raise important points but I don't think this question is the proper forum for them. Best - GLT
    – Geoffrey Thomas
    Jan 12, 2020 at 13:00

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